STEVE INSKEEP, HOST:
Last year, 2012, the Earth experienced a record melt of Arctic ice, torrential rainfall in Australia, and withering droughts in the United States and elsewhere. Scientists are beginning to figure out why. Here's NPR's Richard Harris
RICHARD HARRIS, BYLINE: The Earth is warmer now than it used to be and most Earth scientists say that human beings are largely responsible for that. But it's much harder to determine how much climate change is responsible for specific extreme events. Peter Stott at Britain's Weather Service says researchers are starting to be able to measure a human role in some cases.
PETER STOTT: We've got some new evidence here that human influence on climate has changed the risk and has changed it enough that we can detect it.
HARRIS: Scientists studying some of last year's big weather events say some are more severe than they would have been in the absence of climate change. They say humans accelerated the melting of Arctic ice and also contributed to record-breaking summer heat in the United States. But the drought that came with that heat was simply due to a natural fluctuation in the weather.
These results are published in the "Bulletin of the American Meteorological Society." Richard Harris, NPR News. Transcript provided by NPR, Copyright NPR.